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As a common disease, canker seriously affects the yield and quality of fragrant pear due to the lack of effective control measures. Some fungi have been reported to harbor rich reservoirs of viral resources, and some mycoviruses can be used as biocontrol agents against plant diseases. In this study, 199 isolates were obtained from diseased branches of fragrant pear in the main production areas of Xinjiang. Among them, 134 belonged to Valsa spp., identified using morphological and molecular biological techniques, in which V. mali was the dominant species. The mycoviruses in Valsa spp. were further identified using metatranscriptomic sequencing and RT-PCR. The results revealed that a total of seven mycoviruses were identified, belonging to Botourmiaviridae, Endornaviridae, Fusariviridae, Hypoviridae, Mitoviridae, and Narnaviridae, among which Phomopsis longicolla hypovirus (PlHV) was dominant in all the sample collection regions. The Cryphonectria hypovirus 3-XJ1 (CHV3-XJ1), Botourmiaviridae sp.-XJ1 (BVsp-XJ1), and Fusariviridae sp.-XJ1 (Fvsp-XJ1) were new mycoviruses discovered within the Valsa spp. More importantly, compared with those in the virus-free Valsa spp. strain, the growth rate and virulence of the VN-5 strain co-infected with PlHV and CHV3-XJ1 were reduced by 59% and 75%, respectively, and the growth rate and virulence of the VN-34 strain infected with PlHV were reduced by 42% and 55%, respectively. On the other hand, the horizontal transmission efficiency of PlHV decreased when PlHV was co-infected with CHV3-XJ1, indicating that PlHV and CHV3-XJ1 were antagonistic. In summary, the mycoviruses in Valsa spp. were identified in Xinjiang for the first time, and three of them were newly discovered mycoviruses, with two strains yielding good results. These results will offer potential biocontrol resources for managing pear canker disease and provide a theoretical basis for the control of fruit tree Valsa canker disease. [ABSTRACT FROM AUTHOR]

Many plant diseases are caused by phytopathogenic bacteria which greatly determine the quality of plant production. The biological control of plant pathogenic bacteria is an alternative method to the application of chemicals, which may be accomplished through the destruction of existing inoculums, exclusion from the host, or the suppression or displacement of the pathogen after infection. It offers an environmentally friendly approach to the management of plant disease and can be incorporated with cultural and physical control and limited chemical usage for an effective and integrated disease-management system. Biological control includes the use of beneficial microorganisms, such as specialized fungi and bacteria, to attack and control plant pathogens and the diseases they cause. Biological control is an innovative, cost effective and eco-friendly approach for control of many plant diseases. Bacteria of the genus Bacillus has showed antimicrobial activity against plant pathogenic microorganisms. Bacillus spp. are natural inhabitants of the phyllosphere and rhizosphere. These bacteria are involved in the control of plant diseases through a variety of mechanisms of action, such as competition, systemic resistance induction and antibiotic production. The mechanism of antibiosis has been shown to be one of the most important. Bacillus spp. have the advantage of being already adapted to the environment where they can be applied as biological control. They have the characteristics of having high thermal tolerance, showing rapid growth in liquid culture, and readily form resistant spores. It is considered safe biological agents and their potential as biocontrol agents is considered to be high. This research is based on the isolation and screening of biocontrol activities of soil Bacillus sp. against several phytopathogens in in vitro study. Since tested isolate has showed the production of antimicrobials against the growth of selected phytopathogens, in further work, all of this trial need to be supported by evaluation of antimicrobial activity in in vivo. [ABSTRACT FROM AUTHOR]

Background: Disease suppressiveness of soils to fungal root pathogens is typically induced in the field by repeated infections of the host plant and concomitant changes in the taxonomic composition and functional traits of the rhizosphere microbiome. Here, we studied this remarkable phenomenon for Bipolaris sorokiniana in two wheat cultivars differing in resistance to this fungal root pathogen. Results: The results showed that repeated exposure of the susceptible wheat cultivar to the pathogen led to a significant reduction in disease severity after five successive growth cycles. Surprisingly, the resistant wheat cultivar, initially included as a control, showed the opposite pattern with an increase in disease severity after repeated pathogen exposure. Amplicon analyses revealed that the bacterial families Chitinophagaceae, Anaerolineaceae and Nitrosomonadaceae were associated with disease suppressiveness in the susceptible wheat cultivar; disease suppressiveness in the resistant wheat cultivar was also associated with Chitinophagaceae and a higher abundance of Comamonadaceae. Metagenome analysis led to the selection of 604 Biosynthetic Gene Clusters (BGCs), out of a total of 2,571 identified by AntiSMASH analysis, that were overrepresented when the soil entered the disease suppressive state. These BGCs are involved in the biosynthesis of terpenes, non-ribosomal peptides, polyketides, aryl polyenes and post-translationally modified peptides. Conclusion: Combining taxonomic and functional profiling we identified key changes in the rhizosphere microbiome during disease suppression. This illustrates how the host plant relies on the rhizosphere microbiome as the first line of defense to fight soil-borne pathogens. Microbial taxa and functions identified here can be used in novel strategies to control soil-borne fungal pathogens. [ABSTRACT FROM AUTHOR]

Summary: Age‐related resistance to microbe invasion is a commonly accepted concept in plant pathology. However, the impact of such age‐dependent interactive phenomena is perhaps not yet sufficiently recognized by the broader plant science community. Toward cataloging an understanding of underlying mechanisms, this review explores recent molecular studies and their relevance to the concept. Examples describe differences in genetic background, transcriptomics, hormonal balances, protein‐mediated events, and the contribution by short RNA‐controlled gene silencing events. Throughout, recent findings with viral systems are highlighted as an illustration of the complexity of the interactions. It will become apparent that instead of uncovering a unifying explanation, we unveiled only trends. Nevertheless, with a degree of confidence, we propose that the process of plant age‐related defenses is actively regulated at multiple levels. The overarching goal of this control for plants is to avoid a constitutive waste of resources, especially at crucial metabolically draining early developmental stages. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum is the causal agent of bacterial wilt, one of the most destructive diseases of solanaceous plants, affecting staple crops worldwide. The bacterium survives in water, soil, and other reservoirs, and is difficult to control. In this sense, the use of three specific lytic R. solanacearum bacteriophages was recently patented for bacterial wilt biocontrol in environmental water and in plants. To optimize their applications, the phages and the bacterium need to be accurately monitored and quantified, which is laborious and time-consuming with biological methods. In this work, primers and TaqMan probes were designed, and duplex and multiplex real-time quantitative PCR (qPCR) protocols were developed and optimized for the simultaneous quantification of R. solanacearum and their phages. The quantification range was established from 108 to 10 PFU/mL for the phages and from 108 to 102 CFU/mL for R. solanacearum. Additionally, the multiplex qPCR protocol was validated for the detection and quantification of the phages with a limit ranging from 102 targets/mL in water and plant extracts to 103 targets/g in soil, and the target bacterium with a limit ranging from 103 targets/mL in water and plant extracts to 104 targets/g in soil, using direct methods of sample preparation. [ABSTRACT FROM AUTHOR]

Generally, advancements in various branches of science and technology have had a significant impact on various aspects of plant pathology like efficient pathogen detection. Nanotechnology is found to have many applications of which plant pathology is the one important field. In recent years, nanotechnology has been increasingly applied to the development of novel antimicrobials for the management of pathogenic bacteria affecting agricultural crops. This review discusses the applications of different nanoparticles in plant disease management and their mode of action against the bacteria. The synthesis of nanoparticles (NPs) using biomolecules (protein, enzyme, DNA and plant extracts) have opened a new avenue of research in green nanobiotechnology. They are proved to be effective, cheap and eco-friendly in combating microbes. Reactive oxygen species production, lipid peroxidation, protein oxidation, ATP depletion and DNA degradation are some of the mechanisms by which nanomaterials used to kill bacteria. [ABSTRACT FROM AUTHOR]

Summary: Plant diseases are an important threat to food production. While major pathogenicity determinants required for disease have been extensively studied, less is known on how pathogens thrive during host colonization, especially at early infection stages.Here, we used randomly barcoded‐transposon insertion site sequencing (RB‐TnSeq) to perform a genome‐wide screen and identify key bacterial fitness determinants of the vascular pathogen Xanthomonas campestris pv campestris (Xcc) during infection of the cauliflower host plant (Brassica oleracea). This high‐throughput analysis was conducted in hydathodes, the natural entry site of Xcc, in xylem sap and in synthetic media.Xcc did not face a strong bottleneck during hydathode infection. In total, 181 genes important for fitness were identified in plant‐associated environments with functional enrichment in genes involved in metabolism but only few genes previously known to be involved in virulence. The biological relevance of 12 genes was independently confirmed by phenotyping single mutants. Notably, we show that XC_3388, a protein with no known function (DUF1631), plays a key role in the adaptation and virulence of Xcc possibly through c‐di‐GMP‐mediated regulation.This study revealed yet unsuspected social behaviors adopted by Xcc individuals when confined inside hydathodes at early infection stages. [ABSTRACT FROM AUTHOR]

Massoia lactone could be released from liamocins produced by Aureobasidium melanogenum M39. The obtained Massoia lactone was very stable and highly active against many fungal crop pathogens which cause many plant diseases and food unsafety. Massoia lactone treatment not only could effectively inhibit their hyphal growth and spore germination, but also caused pore formation in cell membrane, reduction of ergosterol content, rise in intracellular ROS levels, and leakage of intracellular components, consequently leading to cellular necrosis and cell death. The direct contact of Massoia lactone with Fusarium graminearum spores could stop the development of Fusarium head blight symptom in the diseased wheats. Therefore, Massoia lactone could be a promising candidate for development as an effective and green bio-fungicide because of its high anti-fungal activity and the multiplicity of mode of its action. [ABSTRACT FROM AUTHOR]

Bacterial endophytes are plant-associated microorganisms colonizing internal tissues without causing any symptoms to their hosts. Their intimate relation with the plant can trigger several beneficial traits for their host, such as growth improvement and tolerance to some biotic and abiotic factors. Therefore, endophytic bacteria can be used as agro-inoculants in various crops suitable for organic production, such as sweet potato. The aim of this study is to reveal the potential use of bacterial endophytes as biocontrol agents against sweet potato pathogens. Selected endophytic bacterial strains revealed antifungal activity against important tuber, root and stem pathogens, belonging to Fusarium, Botrytis, Curvularia and Trichothecium genera. [ABSTRACT FROM AUTHOR]

Multiple infections, either simultaneous or sequential, affecting a single plant or crop are now recognized to be common in plant disease epidemics. These multiple infections thus generate a range of competitive interactions (exploitation competition, apparent competition, or interference competition) that directly impact competitors' life history traits, and hence fitness. While a theoretical framework, based primarily on three ecological theories—niche exclusion, the "tragedy of the commons", and the virulence–transmission trade‐off, provides insights into potential outcomes of multiple infections on pathogen evolution and virulence and on disease dynamics, experimental observations, although rather rare so far, strongly suggest that unexpected outputs can also occur. This review therefore attempts to provide a comprehensive overview of both theoretical and empirical knowledge about multiple infection in plants. It highlights the need for a detailed assessment of pathogen life history traits and their modulation according to competition types, host receptivity, and pathogen life strategies for a better understanding and prediction of the evolutionary and demographic outcomes of multiple infections, as well as research questions still open in this emerging field of plant pathology. [ABSTRACT FROM AUTHOR]

Pathogenic microorganisms are one of the main environmental factors causing biological diseases, and their rapid spread and variety may lead to the outbreak of animal infectious diseases or plant diseases. However, the air environment is complex, the pathogen fungal infectious disease outbreak early concentration is low and the shape and size is small. There is a lack of rapid, accurate, portable and low-cost early detection methods for pathogenic fungi. Here, we construct a multispectral diffraction microfluidic sensing system for pathogenic fungi. Firstly, a microfluidic chip with the function of targeted purification of pathogenic fungi was designed, and the diffraction fingerprint of purified pathogenic fungi was collected on the chip. By analyzing the light diffraction spectrum, the morphological and absorption characteristics of different fungi at different wavelengths were obtained, and different kinds of pathogenic microorganisms in complex environment were identified. Then, seven weighting schemes were compared to select the characteristic wavelength that best reflects spore differences. Dispersion intensity compared of fingerprint (DICF) and Relative superimposed light intensity (RSLI) were defined as training indexes. To obtain higher recognition accuracy, two parameters of cluster centroid distance and dispersion are defined as evaluation indexes. Finally, 5 kinds of pathogenic fungi and particles with similar characteristics were selected for experimental verification, and the identification accuracy was 98.7%. We can foresee potential applications for this approach in disease control and environmental monitoring of airborne pathogens. • Pathogenic fungi in complex environment are low in concentration, which is difficult to capture and distinguish. • The microfluidic chip is designed to integrate separation, enrichment, detection and verification on chip. • The multi-spectral diffraction sensing system enables rapid and accurate identification of pathogenic bacteria. • It has a broad prospect in restraining the recessive spread of pathogenic microorganisms and environmental monitoring. [ABSTRACT FROM AUTHOR]

Real-time PCR (Polymerase Chain Reaction) or qPCR is a method by which the amount of the PCR product can be determined in real-time, and is very useful for investigating gene expression. The main advantages of qPCR are that it provides fast and high-throughput detection and quantification of target DNA sequences in different matrices. The lower time of amplification is facilitated by the simultaneous amplification and visualization of newly formed DNA amplicons. The development and application of molecular methods for the detection of pathogens has significantly changed the diagnosis and control of plant diseases, various environmental samples, including hosts tissues, soil, water and air. With real-time PCR method, it is possible not only to identify and detect the presence or absence of the target pathogen, but it is also possible to quantify the amount present in the sample allowing the quantitative assessment of the number of the pathogen in the sample. Detection and accurate identification of plant pathogens is one of the most important strategies for controlling plant diseases to initiate preventive or curative measures. Plum pox virus (PPV), the agent of sharka, is the most devastating virus infecting stone fruits. The PPV control is mainly based on prevention, and its quick and reliable detection is considered crucial in this strategy. In this study DAS-ELISA and real-time PCR were compared for evaluating their potentialities and limits for large scale surveys. Plum (Prunus domestica L.) hosts and apricot (Prunus armeniaca L.) samples from several different locations were included in laboratory test analyzes, plant organs (phloem, buds, flowers, leaves and fruits) and parts of them, different seasons (spring, summer and winter period 2017/20), presence or absence of symptoms were considered for comparison. Using DAS-ELISA tests and a universal set of antibodies (BIOREBA), have proved the presence of virus of Plum pox in all examined samples, especially from samples collected in summer, but also in virus status examination in winter and early spring season. The examination found high concentrations of viral antigens in plant samples (OD 2.912-2.752, for 30 min / 405 nm). Real-time PCR show amplification plot for positive PPV samples on plums and apricot. [ABSTRACT FROM AUTHOR]

Stress caused by pathogens strongly damages plants. Developing products to control plant disease is an important challenge in sustainable agriculture. In this study, a heat-killed endophytic bacterium (HKEB), Bacillus aryabhattai, is used to induce plant defense against fungal and bacterial pathogens, and the main defense pathways used by the HKEB to activate plant defense are revealed. The HKEB induced high protection against different pathogens through the salicylic and jasmonic acid pathways. We report the presence of gentisic acid in the HKEB for the first time. These results show that HKEBs may be a useful tool for the management of plant diseases. [ABSTRACT FROM AUTHOR]

Strawberry crown rot is one of the most important diseases in Ecuador, with an incidence of up to 70% in the field. In the world, the strawberry crown rot is caused by different etiological agents, which makes efficient control of the disease difficult. In this study, 12 samples of strawberry plants were collected, at different stages of disease development, to determine the causative agent in Ecuador. The fungal isolates, consistent with the isolation, were identified and characterized using molecular and morphological approaches, and finally, Koch’s postulate was carried out. Based on the form of growth, mycelial color, conidial morphology, and molecular characteristics (sequencing of the ITS and EF-1α region), the pathogen associated with the symptoms showed 99% similarity with the species Neopestalotiopsis mesopotamica. The result of Koch’s postulates showed symptoms similar to those observed in field plants, in addition, the same inoculated isolate was recovered from artificially inoculated tissues. This is the first report of this fungus causing strawberry crown rot in Ecuador and in the world. [ABSTRACT FROM AUTHOR]

Aims: Determining the soil factors that drive the dynamics of soil-borne pathogens is an essential step toward the formulation and implementation of strategies for the control of plant diseases. Methods: We sampled 48 healthy and infected soils in peanut fields from six counties in Eastern China to explore the relationships between soil multifunctionality, microbial communities, and peanut stem rot pathogen, Athelia rolfsii. Results: The results showed that peanut stem rot infection did not affect soil microbial richness, but it increased soil multifunctionality, altered the microbial community composition, and decreased the complexity of microbial co-occurrence networks significantly. Soil biotic and abiotic factors had markedly effects on A. rolfsii, and specific soil functions and microbial taxa were significantly associated with A. rolfsii abundance. Soil multifunctionality and microbial community compositions negatively affected A. rolfsii abundance, while the effects of bacterial and fungal richness were contrasting for healthy and infected soils. Longitude and latitude indirectly and positively affected A. rolfsii abundance. Conclusions: The results demonstrate that soil multifunctionality and microbial communities play a vital role in regulating the dynamics of peanut stem rot pathogen, which could enhance our understanding of the relationships between soil factors, pathogen dynamics, and plant health. [ABSTRACT FROM AUTHOR]

The transition toward sustainable agriculture requires rethinking cropping systems in the light of less intensive and chemically reliant practices. Weed management is one of the target practices to evolve cropping systems with decreased impact on the environment. While softened management will lead to increased weeds/crops coexistence, it is of importance to assess the relative benefits and drawbacks of new practices. Among the potential drawbacks of weeds/crops coexistence, disease risk may increase if weeds are hosting pathogens. In this study, we assessed the potential of weeds for hosting pathogenic generalist fungi known to translate into disease in crops. We first describe prevalence in fields after harvest and relate prevalence to species characteristics and communities. Then, we directly test the idea that weeds serve as inoculums sources during cropping with a natural experiment. This study highlights variation in host skill among feral weeds for Colletotrichum species, including potential congeneric sub-specialization on different weeds within communities. Last, prevalence within fields was more correlated to focal crop inoculation rates compared to local weed load, but there was a significant correlation effect with prevalence on weeds in the vicinity of fields, suggesting that weeds are mediating disease levels at the local scale, too. Results pointed to the importance of weed host skill in disease risk yet open the door to the potential control of pathogens via targeted weed management. [ABSTRACT FROM AUTHOR]

Stem rust caused by Puccinia graminis f. sp. tritici is an important disease of wheat in the world. This disease is also common in the Sinop province of Turkey. The pathogen forms new races and these races may overcome the resistance present in wheat cultivars. For sustainable wheat production, identification of the stem races is necessary. During 2016 and 2017, surveys were conducted in wheat-growing areas of Sinop province and from diseased plants, 42 single uredospore pustule isolates were obtained. Using North American differential genotypes stem rust races were identified. The most common race was TTTTF followed by TTKTF, RTTTF, RTKTF, and TTKTC. [ABSTRACT FROM AUTHOR]

Xylem vascular wilt pathogens cause devastating diseases in plants. Proliferation of these pathogens in the xylem causes massive disruption of water and mineral transport, resulting in severe wilting and death of the infected plants. Upon reaching the xylem vascular tissue, these pathogens multiply profusely, spreading vertically within the xylem sap, and horizontally between vessels and to the surrounding tissues. Plant resistance to these pathogens is very complex. One of the most effective defense responses in resistant plants is the formation of physico-chemical barriers in the xylem tissue. Vertical spread within the vessel lumen is restricted by structural barriers, namely, tyloses and gels. Horizontal spread to the apoplast and surrounding healthy vessels and tissues is prevented by vascular coating of the colonized vessels with lignin and suberin. Both vertical and horizontal barriers compartmentalize the pathogen at the infection site and contribute to their elimination. Induction of these defenses are tightly coordinated, both temporally and spatially, to avoid detrimental consequences such as cavitation and embolism. We discuss current knowledge on mechanisms underlying plant-inducible structural barriers against major xylem-colonizing pathogens. This knowledge may be applied to engineer metabolic pathways of vascular coating compounds in specific cells, to produce plants resistant towards xylem colonizers. [ABSTRACT FROM AUTHOR]

Biological control is described as the suppression of one or more populations of plant pathogens using introduced or resident living species rather than disease-resistant host plants. This can be accomplished by the use of microbial biological control agents (MBCAs) where they biologically control plant pathogens interacting with their hosts via a range of modes of action. Overuse of pesticides has had a negative impact on the climate in recent decades that gave rise to human health issues. This posed a dire need to explore alternative strategies that are comparatively safe, environmental, and monetarily feasible. The employment of MBCAs is found to be a highly effective way to regulate several diseases of the exiting flora caused mainly by nematode infestation and bacterial or fungal pathogens. Microbial inoculants suppress a particular form of plant disease or regulate soils so that plant-associated species and native soil can work together to suppress the disease. Microbes, such as bacteria, protozoa, algae, and fungi, frequently interact with plants in several ways including protocooperation, mutualism, commensalism, rivalry, neutralism, amensalism, predation, and parasitism. These interactions are cascades of highly regulated metabolic events that combine various kinds of action. Compounds such as enzymes, signaling compounds, and other interfering metabolites are released in situ at low levels during the interaction. Pseudomonas, Erwinia, Bacillus, Agrobacterium, Rahnella, Lysobacter, Myxobacteria, Enterobacter, and Streptomyces are some of the bacterial genera that have major biocontrol potential to mitigate crop plant diseases. Several species, including P. fluorescens, P. putida, P. cepacia, P. aureofaciens, P. tolaasii, P. fluorescens (strains A1, BK1, TL3B1, A506, and B10), Erwinia herbicola, B. cereus (strain UW85), Agrobacterium radiobacter (strain K84), Rahnella aquatilis have been proved beneficial against various crop diseases. Likewise, Trichoderma harzianum, Glomus fasciculatum, G. macrocarpum, and Pisolithus tinctorius are known to induce plant defense response against phytotoxic effects caused by different pathogenic strains. This review highlights the role of MBCAs against pathogenic microorganisms and their mode of action in terms of the ability to enhance plant defense systems for their improved growth. [ABSTRACT FROM AUTHOR]

To fight against pathogens, defense systems in plants mainly depend upon preformed as well as induced responses. Pathogen detection activates induced responses and signals are transmitted for coordinated cellular events in order to restrict infection and spread. In spite of significant developments in manipulating genes, transcription factors and proteins for their involvement in immunity, absolute tolerance/resistance to pathogens has not been seen in plants/crops. Defense responses, among diverse plant types, to different pathogens involve modifications at the physio-biochemical and molecular levels. Secreted by oomycetes, elicitins are small, highly conserved and sterol-binding extracellular proteins with PAMP (pathogen associated molecular patterns) functions and are capable of eliciting plant defense reactions. Belonging to multigene families in oomycetes, elicitins are different from other plant proteins and show a different affinity for binding sterols and other lipids. These function for sterols binding to catalyze their inter-membrane and intra- as well as inter-micelle transport. Importantly, elicitins protect plants by inducing HR (hypersensitive response) and systemic acquired resistance. Despite immense metabolic significance and the involvement in defense activities, elicitins have not yet been fully studied and many questions regarding their functional activities remain to be explained. In order to address multiple questions associated with the role of elicitins, we have reviewed the understanding and topical advancements in plant defense mechanisms with a particular interest in elicitin-based defense actions and metabolic activities. This article offers potential attributes of elicitins as the biological control of plant diseases and can be considered as a baseline toward a more profound understanding of elicitins. [ABSTRACT FROM AUTHOR]

Summary: Interactions between pathogenic microorganisms and their hosts are varied and complex, encompassing open‐field scale interactions to interactions at the molecular level. The capacity of plant pathogenic bacteria and fungi to cause diseases in human and animal systems was, until recently, considered of minor importance. However, recent evidence suggests that animal and human infections caused by plant pathogenic fungi, bacteria and viruses may have critical impacts on human and animal health and safety. This review analyses previous research on plant pathogens as causal factors of animal illness. In addition, a case study involving disruption of type III effector‐mediated phagocytosis in a human cell line upon infection with an opportunistic phytopathogen, Pseudomonas syringae pv. tomato, is discussed. Further knowledge regarding the molecular interactions between plant pathogens and human and animal hosts is needed to understand the extent of disease incidence and determine mechanisms for disease prevention. [ABSTRACT FROM AUTHOR]

Summary: Tolerance and resistance represent two strategies that hosts evolved to protect themselves from pathogens. Tolerance alleviates the reduction in host fitness due to infection without reducing a pathogen's growth, whereas resistance reduces pathogen growth. We investigated the tolerance of wheat to the major fungal pathogen Zymoseptoria tritici in 335 elite wheat cultivars.We used a novel digital phenotyping approach that included 11 152 infected leaves and counted 2069 048 pathogen fruiting bodies.We discovered a new component of tolerance that is based on the relationship between the green area remaining on a leaf and the number of pathogen fruiting bodies. We found a negative correlation between tolerance and resistance among intolerant cultivars, presenting the first compelling evidence for a tradeoff between tolerance and resistance to plant pathogens. Surprisingly, the tradeoff arises due to limits in the host resources available to the pathogen and not due to metabolic constraints, contrary to what ecological theory suggests.The mechanism underlying this tradeoff may be relevant for many plant diseases in which the amount of host resources available to the pathogen can limit the pathogen population. Our analysis indicates that European wheat breeders may have selected for tolerance instead of resistance to an important pathogen. [ABSTRACT FROM AUTHOR]

Citrus crops have great economic importance worldwide. However, citrus production faces many diseases caused by different pathogens, such as bacteria, oomycetes, fungi and viruses. To overcome important plant diseases in general, new technologies have been developed and applied to crop protection, including RNA interference (RNAi) and clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas) systems. RNAi has been demonstrated to be a powerful tool for application in plant defence mechanisms against different pathogens as well as their respective vectors, and CRISPR/Cas system has become widely used in gene editing or reprogramming or knocking out any chosen DNA/RNA sequence. In this article, we provide an overview of the use of RNAi and CRISPR/Cas technologies in management strategies to control several plants diseases, and we discuss how these strategies can be potentially used against citrus pathogens. [ABSTRACT FROM AUTHOR]

As the occurrence and severity of soil-borne diseases are strongly season-dependent, the ecological processes that shift plant microbiome compositions and functions upon pathogen infection in different seasons are rarely studied. In this study, we compared the differences in fungal and bacterial communities in rhizosphere soil between healthy and diseased bamboo plants throughout the four seasons at the main bamboo production site in China and investigated how basal rot disease caused by Fusarium proliferatum affected the composition, structure and ecological functions of rhizosphere-associated microorganisms. The results showed that diseased bamboo plants enriched the highest abundance of Fusarium genus in rhizosphere soil while receiving largely increased stem lesion area in summer. Microbiome analysis further proved that healthy bamboo plants harbored more ecologically beneficial microbial taxa that might function as biological protectants in their rhizosphere soil than diseased plants at the same season. Three individual strains with biocontrol potentials were further isolated and identified as Trichoderma spirale, Bacillus velezensis and Streptomyces mirabilis. The antagonistic tests further demonstrated their inhibition effects on the growth and pathogenicity of the pathogenic fungus F. proliferatum in vitro and in vivo. This study advances our understanding of soil-borne pathogen mediated changes in microbiome structure and function in plant rhizosphere soil and provides potential biocontrol strains for increasing plant resistance against basal rot disease. • The rhizosphere soil of diseased plants enriched the highest abundance of Fusarium genus in summer. • The stem lesion area of diseased plants was largely increased in summer. • Healthy plants harbored more ecologically beneficial microbes than diseased plants. • The biocontrol strains were identified as Trichoderma spirale, Bacillus velezensis and Streptomyces mirabilis. • The antagonistic effects of the strains against pathogen were tested in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Plant defense against pathogens includes a range of mechanisms, including, but not limited to, genetic resistance, pathogen‐antagonizing endophytes, and pathogen competitors. The relative importance of each mechanism can be expressed in a hierarchical view of defense. Several recent studies have shown that pathogen antagonism is inconsistently expressed within the plant defense hierarchy. Our hypothesis is that the hierarchy is governed by contingency rules that determine when and where antagonists reduce plant disease severity.Here, we investigated whether pathogen competition influences pathogen antagonism using Populus as a model system. In three independent field experiments, we asked whether competition for leaf mesophyll cells between a Melampsora rust pathogen and a microscopic, eriophyid mite affects rust pathogen antagonism by fungal leaf endophytes. The rust pathogen has an annual, phenological disadvantage in competition with the mite because the rust pathogen must infect its secondary host in spring before infecting Populus. We varied mite–rust competition by utilizing Populus genotypes characterized by differential genetic resistance to the two organisms. We inoculated plants with endophytes and allowed mites and rust to infect plants naturally.Two contingency rules emerged from the three field experiments: (a) Pathogen antagonism by endophytes can be preempted by host genes for resistance that suppress pathogen development, and (b) pathogen antagonism by endophytes can secondarily be preempted by competitive exclusion of the rust by the mite.Synthesis: Our results point to a Populus defense hierarchy with resistance genes on top, followed by pathogen competition, and finally pathogen antagonism by endophytes. We expect these rules will help to explain the variation in pathogen antagonism that is currently attributed to context dependency. [ABSTRACT FROM AUTHOR]

Summary: Dothistroma needle blight is one of the most devastating pine tree diseases worldwide. New and emerging epidemics have been frequent over the last 25 years, particularly in the Northern Hemisphere, where they are in part associated with changing weather patterns. One of the main Dothistroma needle blight pathogens, Dothistroma septosporum, has a global distribution but most molecular plant pathology research has been confined to Southern Hemisphere populations that have limited genetic diversity. Extensive genomic and transcriptomic data are available for a D. septosporum reference strain from New Zealand, where an introduced clonal population of the pathogen predominates. Due to the global importance of this pathogen, we determined whether the genome of this reference strain is representative of the species worldwide by sequencing the genomes of 18 strains sampled globally from different pine hosts. Genomic polymorphism shows substantial variation within the species, clustered into two distinct groups of strains with centres of diversity in Central and South America. A reciprocal chromosome translocation uniquely identifies the New Zealand strains. Globally, strains differ in their production of the virulence factor dothistromin, with extremely high production levels in strain ALP3 from Germany. Comparisons with the New Zealand reference revealed that several strains are aneuploids; for example, ALP3 has duplications of three chromosomes. Increased gene copy numbers therefore appear to contribute to increased production of dothistromin, emphasizing that studies of population structure are a necessary adjunct to functional analyses of genetic polymorphisms to identify the molecular basis of virulence in this important forest pathogen. [ABSTRACT FROM AUTHOR]

Myrtle rust poses a significant biosecurity threat to Australia with potential for long‐term damaging impacts on native flora and plant industries. This study describes the disease cycle of Austropuccinia psidii, the myrtle rust pathogen, in Eucalyptus globulus and Eucalyptus obliqua, two commercially and ecologically important species from different subgenera of Eucalyptus. Ontogeny and morphology of infection structures of A. psidii on plants of both Eucalyptus species with different rust response phenotypes, i.e. completely resistant, hypersensitive and highly susceptible, were investigated. Plants were inoculated with single‐uredinium‐derived urediniospores and examined by scanning electron microscopy. No differences between rust response phenotypes were observed in germination of urediniospores, formation of appressoria or length of germ tubes. The growth of germ tubes had no affinity towards stomata of either species. Histological observations indicated direct penetration by infection pegs through the leaf cuticle and no penetration beyond the epidermis on rust‐resistant E. obliqua. Eucalyptus obliqua plants that were identified as susceptible to A. psidii at 3‐ and 6‐months‐old showed no disease when reinoculated with A. psidii at 12‐months‐old; this indicated possible early acquisition of adult plant resistance to A. psidii in this species. In the susceptible phenotype of E. globulus rust inoculation led to rapid colonization of leaf parenchyma cells with the disease cycle completed within 10 days. These findings provide valuable insights into host–pathogen interactions in the Eucalyptus–A. psidii pathosystem, which might be useful for the development of effective rust control strategies across Eucalyptus subgenera. [ABSTRACT FROM AUTHOR]

Biofilm is a mode of living employed by many pathogenic and environmental microbes to proliferate as multicellular aggregates on inert inanimate or biological substrates. Several microbial diseases are associated with biofilms that pose challenges in treatment with antibiotics targeting individual cells. Bacteria in biofilms secrete exopolymeric substances that contribute to architectural stability and provide a secure niche to inhabiting cells. Quorum sensing (QS) plays essential roles in biofilm development. Pathogenic bacteria in biofilms utilize QS mechanisms to activate virulence and develop antibiotic resistance. This review is a brief overview of biofilm research and provides updates on recent understandings on biofilm development, antibiotic resistance and transmission, and importance of QS mechanisms. Strategies to combat biofilm associated diseases including anti-biofilm substances, quorum quenching molecules, bio-surfactants and competitive inhibitors are briefly discussed. The review concludes with updates on recent approaches utilized for biofilm inhibition and provides perspectives for further research in the field. [ABSTRACT FROM AUTHOR]

Elsinoë fawcettii, E. australis, and Pseudocercospora angolensis are causal agents of citrus scab and spot diseases. The three pathogens are listed as quarantine pests in many countries and are subject to phytosanitary measures to prevent their entry. Diagnosis of these diseases based on visual symptoms is problematic, as they could be confused with other citrus diseases. Isolation of E. fawcettii, E. australis, and P. angolensis from infected tissues is challenging because they grow slowly on culture media. This study developed rapid and specific detection tools for the in planta detection of these pathogens, using either conventional PCR or one-tube multiplex real-time PCR. Primers and hybridization probes were designed to target the single-copy protein-coding gene MS204 for E. fawcettii and E. australis and the translation elongation factor (Tef-1a) gene for P. angolensis. The specificity of the assays was evaluated by testing against DNA extracted from a large number of isolates (102) collected from different citrus-growing areas in the world and from other hosts. The newly described species E. citricola was not included in the specificity test due to its unavailability from the CBS collection. The detection limits of conventional PCR for the three pathogens were 100, 100, and 10 pg µl-1 gDNA per reaction for E. fawcettii, E. australis, and P. angolensis, respectively. The quadruplex qPCR was fully validated assessing the following performance criteria: sensitivity, specificity, repeatability, reproducibility, and robustness. The quadruplex real-time PCR proved to be highly sensitive, detecting as low as 243, 241, and 242 plasmidic copies (pc) µl-1 of E. fawcettii, E. australis, and P. angolensis, respectively. Sensitivity and specificity of this quadruplex assay were further confirmed using 176 naturally infected citrus samples collected from Ethiopia, Cameroon, the United States, and Australia. The quadruplex assay developed in this study is robust, cost-effective, and capable of high-throughput detection of the three targets directly from citrus samples. This new detection tool will substantially reduce the turnaround time for reliable species identification and allow rapid response and appropriate action. [ABSTRACT FROM AUTHOR]

In Kagawa Prefecture, Japan, the pathogens Phytophthora pseudolactucae, Pythium irregulare, Pythium uncinulatum, and Pythium spinosum have caused huge losses in lettuce production. We used loop-mediated isothermal amplification (LAMP) to analyze soil and plants in lettuce fields for the presence of these four pathogens. To develop an effective on-site detection method, we contrasted the Plant-LAMP and Plant Culture-LAMP procedures for plant samples, and five soil DNA extraction methods for soil samples. Plant-LAMP and a Soil DNA Isolation kit were selected to analyze three fields for the pathogen species present, infected sites, and level of soil contamination. We found that the same wilting symptoms could be caused by Phytophthora or Pythium, or a mixture of species from both genera. Ph. pseudolactucae infects the pith of the lettuce in aboveground parts, whereas Pythium spp. mainly infect roots. Ph. pseudolactucae and Py. uncinulatum caused disease more frequently than the other two pathogens. Furthermore, not all of the pathogens existed in the soil near infected lettuce plants. Therefore, the LAMP method can be used to diagnose pathogenic oomycetes in the field, and will be useful in the development of control strategies in lettuce production. [ABSTRACT FROM AUTHOR]

A rapid, sensitive and visual loop‐mediated isothermal amplification (LAMP) method for detecting Acidovorax citrulli in cucurbit seed was developed in this study. The LAMP primers were designed to recognize the non‐ribosomal peptide synthetase (NRPS) gene (locus tag: Aave_4658) from A. citrulli. The LAMP assay was conducted at 64°C in 1 hr with calcein as an indicator. The sensitivity and specificity of the LAMP assay were further compared with those of a conventional polymerase chain reaction (PCR). The LAMP assay is highly specific to A. citrulli, and no cross‐reaction was observed with other bacterial pathogen. The sensitivity of the LAMP assay was 100‐fold higher than that of conventional PCR with a detection limit of 1 pg of genomic DNA. Using the LAMP assay, 7 of 12 cantaloupe seedlots collected from Xinjiang province were determined to be positive for A. citrulli. In contrast, only 2 of 12 seedlots showed positive for the pathogen with conventional PCR. Moreover, A. citrulli was detected in 100% of artificially infested seedlots with 0.01% infestation or greater. Our results demonstrated that the LAMP assay was simple, visual and sensitive for detecting A. citrulli, especially in seed health testing. Hence, this method has great potential application in routine detecting seed‐borne pathogens and reducing the risk of epidemics. [ABSTRACT FROM AUTHOR]

Weeds are reservoirs for the survival of pathogenic microorganisms and cause of spread of infectious disease of plants through vectors. To minimize the spread of bacteria to other host crops, proper characterization is required to suggest suitable control strategy. Survey was conduct in December 2015, leaf blight was observed on barnyard grass growing in surroundings of citrus orchards located in Lahore, Pakistan. Isolation of the bacterium on nutrient agar medium was performed and their characterization based on morphological and biochemical tests. 16S rRNA was amplified directly with primers 27F/1492R, cloned and sequenced. Sequences were blast in NCBI data base which showed 99% identity to P. agglomerans strain. A neighbor-joining tree was generated with reported bacterial strain that were most closely to isolated strain P. agglomerans (LT592133). Pathogenicity test was conducted on barnyard grass with bacterial suspensions having 1.5 × 108 CFU/ml in controlled conditions to confirm Koch's postulates. According to results this is first report on the incidence of Pantoea agglomerans on Barnyard grass in Pakistan. [ABSTRACT FROM AUTHOR]

Wheat blast, caused by the Magnaporthe oryzae Triticum pathotype, is an economically important fungal disease of wheat. Wheat blast symptoms are similar to Fusarium head scab and can cause confusion in the field. Currently, no in-field diagnostic exists for M. oryzae Triticum. Loop-mediated isothermal amplification (LAMP) primers were designed to target the PoT2 and MoT3 loci, previously shown to be specific for M. oryzae and M. oryzae Triticum, respectively. Specificity was determined using 158 M. oryzae strains collected from infected wheat and other grasses and representing geographic and temporal variation. Negative controls included 50 Fusarium spp. isolates. Sensitivity was assessed using 10-fold serial dilutions of M. oryzae Triticum gDNA. PoT2- and MoT3-based assays showed high specificity for M. oryzae and M. oryzae Triticum, respectively, and sensitivity to approximately 5 pg of DNA per reaction. PoT2 and MoT3 assays were tested on M. oryzae Triticum-infected wheat seed and spikes and identified M. oryzae and M. oryzae Triticum, respectively, using a field DNA extraction kit and the portable Genie II system. The mitochondrial NADH-dehydrogenase (nad5) gene, an internal control for plant DNA, was multiplexed with PoT2 and MoT3 and showed results comparable with individual assays. These results show applicability for M. oryzae Triticum field surveillance, as well as identifying nonwheat species that may serve as a reservoir or source of inoculum for nearby wheat fields. [ABSTRACT FROM AUTHOR]

Bacillus pumilus strain LYMC-3 was isolated from the stem of Pinus massoniana, and its culture filtrate exhibited strong nematicidal activity towards pinewood nematodes (Bursaphelenchus xylophilus). In this study, the nematicidal substance from the culture filtrate of B. pumilus LYMC-3 was isolated using a rotary evaporator, TLC (thin-layer chromatography), silica gel column chromatography, and HPLC. A single nematicidal compound was purified and identified as 2-{3-[(3S,8aS)-1,4-Dioxooctahydropyrrolo[1,2-a] pyrazin-3-yl] propyl}guanidine by LC-MS/MS. The median lethal concentrations (LC50) of the guanidine compound were determined as 113.5 mg L−1 and 62.5 mg L−1 against pinewood nematodes after 24 h and 48 h of treatment, respectively. This study demonstrates the nematicidal activity of the guanidine compound from B. pumilus LYMC-3, and highlights the high potential for the compound to be used in biocontrol of B. xylophilus. [ABSTRACT FROM AUTHOR]

Summary: The health of the Western honey bee is threatened by a global epidemic of deformed wing virus (DWV) infections driven by the ectoparasitic mite Varroa destructor acting as mechanical and biological virus vector. Three different variants of DWV, DWV‐A, ‐B and ‐C exist. Virulence differences between these variants and their relation to V. destructor are still controversially discussed. We performed laboratory experiments to analyze the virulence of DWV directly isolated from crippled bees (DWVP0) or after one additional passage in bee pupae (DWVP1). We demonstrated that DWVP0 was more virulent than DWVP1 for pupae, when pupal mortality was taken as virulence marker, and for adult bees, when neurotropism and cognitive impairment were taken as virulence markers. Phylogenetic analysis supported that DWV exists as quasispecies and showed that DWVP0 clustered with DWV‐B and DWVP1 with DWV‐A when the phylogeny was based on the master sequences of the RNA‐dependent RNA polymerase but not so when it was based on the VP3 region master sequences. We propose that switching of DWV between the bee and the mite host is accompanied by changes in viral sequence, tissue tropism and virulence and that the RNA‐dependent RNA polymerase is involved in determining host range and virulence. [ABSTRACT FROM AUTHOR]

Plants and animals host many microbial symbionts, including both pathogens and mutualists. However, most experimental studies include only one symbiont, and few examine interactions of more than two microbes with their host. Here, we examined whether coinfection with two pathogens causes a synergistic reduction in the benefits that hosts receive from a microbial mutualist. We also measured the effects of a microbial mutualist on the within‐ and between‐host competition between coinfecting pathogens. We manipulated the presence of Clover yellow vein virus (ClYVV), Bean common mosaic virus (BCMV), rhizobia bacteria, and nitrogen fertilizer in common beans (Phaseolus vulgaris). We found asymmetric, context‐dependent interactions among the three microbial symbionts and their host. Coinfection with both viruses led to greater than additive negative effects on the amount of nitrogen that plants received from rhizobia. Rhizobia colonization decreased immune signaling in singly infected plants, but not in coinfected plants. Compared to single ClYVV infection, ClYVV reached higher concentrations within hosts coinfected with BCMV, but only in the presence of rhizobia. Coinfection increased BCMV vertical transmission rates for plants without supplemental nitrogen, but overall vertical transmission opportunities were not affected due to reduced seed production. Examining interactions between multiple microbes sharing a host can reveal important insights about nutrient cycling, disease severity, and pathogen epidemiology. [ABSTRACT FROM AUTHOR]

The study of efficiency of Cyathus spp. to control plant pathogenic bacteria and fungi the results showed that some Cyathus spp. effectively control plant pathogenic bacteria, such as Pectobacteria sp., Pseudomonas sp., Ralstonia solanacearum and Xanthomonas campestris pv. vesicatoria in vitro. The most effective to control Pectobacteria sp. was C. striatus KKU4 with 0.62 cm clear zone diameters. Therefore C. striatus KKU6 could control Pseudomonas sp. with 1.34 cm clear zone diameters, C. pallidus KKUITN2/KKULN2 could control R. solanacearum with 0.85 cm clear zone diameters and C.striatus KKU 5 was the most effective to control X. campestris pv. vesicatoria with 0.29 cm clear zone diameters. The study of antagonistic activity against plant pathogenic fungi by dual culture technique, the results showed that some species could control Fusarium sp. including C. striatus KKU3 and C. earlei KKULP1 with 47.94% and 56.0% inhibition, respectively when placing zero and four days before Fusarium sp. C. stercoreus KKUITP2/KKULP2 and KKUITP3/KKULP3 could control Pythium aphanidermatum when placing before P. aphanidermatum for four days. None of the isolates could control Rhizoctonia solani and Sclerotium rofsii. [ABSTRACT FROM AUTHOR]

Argyrotaenia sphaleropa is a lepidopteran pest in deciduous fruit orchards in Uruguay. The primary control method of these pests is the use of chemical insecticides; however, alternative strategies, friendlier to the environment and compatible with a regional programme of integrated pest management, are definitely needed. Biological control with the use of local entomopathogenic microorganisms could be a sustainable solution. In this study, a biological screening was conducted to characterize spore‐forming bacilli for their capacity to kill larvae of this species. Bacillus thuringiensis, B. pumilus, B. aryabhattai, B. amyloliquefaciens and Lysinibacillus xylanilyticus were identified based on sequence analyses of 16S and partial GyrB gene. Lysinibacilus xylanilyticus showed the highest mortality towards first‐instar larvae fed with diet treated with spore suspensions. Specific virulence factors like proteinaceous parasporal inclusions were observed not only in isolates of B. thuringiensis but also in L. xylanilyticus. Ordering of isolates based on multivariate analysis of putative secondary virulence factors like biosurfactant and biofilm production, haemolytic activity and motility, separated the virulent isolate of L. xylanilyticus. This is the first report of L. xylanilyticus causing mortality in A. sphaleropa or any other member of Lepidoptera. A search for more virulent strains of this species is envisaged. [ABSTRACT FROM AUTHOR]

The phytosanitary emergence triggered by Xylella fastidiosa introduction in Europe urgently calls for research on its main vector, the meadow spittlebug, Philaenus spumarius. The difficulties faced in altering P. spumarius life cycle setting up a continuous indoor rearing under artificial conditions, obtaining a continuous availability of insects for laboratory trials, represent a great limit for research. Here, we propose a methodology to rear P. spumarius in the laboratory allowing the supply of nymphs and adults before they become available in the field. This crucial step forward will permit to overcome the seasonality barrier, reducing time and efforts currently required for experimentation on the meadow spittlebug. The proposed methodology would allow producing the data urgently required to fill the knowledge gap and finally set up an effective and environmentally friendly control strategy of P. spumarius. [ABSTRACT FROM AUTHOR]

Summary: Verticillium wilt, one of the most devastating diseases of cotton (Gossypium hirsutum), causes severe yield and quality losses. Given the effectiveness of plant polygalacturonase‐inhibiting proteins (PGIPs) in reducing fungal polygalacturonase (PG) activity, it is necessary to uncover the key functional amino acids to enhance cotton resistance to Verticillium dahliae. To identify novel antifungal proteins, the selectivity of key amino acids was investigated by screening against a panel of relevant PG‐binding residues. Based on the obtained results, homologous models of the mutants were established. The docking models showed that hydrogen bonds and structural changes in the convex face in the conserved portion of leucine‐rich repeats (LRRs) may be essential for enhanced recognition of PG. Additionally, we successfully constructed Cynanchum komarovii PGIP1 (CkPGIP1) mutants Asp176Val, Pro249Gln, and Asp176Val/Pro249Gln and G. hirsutum PGIP1 (GhPGIP1) mutants Glu169Val, Phe242Gln, and Glu169Val/Phe242Gln with site‐directed mutagenesis. The proteins of interest can effectively inhibit VdPG1 activity and V. dahliae mycelial growth in a dose‐dependent manner. Importantly, mutants that overproduced PGIP in Arabidopsis and cotton showed enhanced resistance to V. dahliae, with reduced Verticillium‐associated chlorosis and wilting. Furthermore, the lignin content was measured in mutant‐overexpressing plants, and the results showed enhanced lignification of the xylem, which blocked the spread of V. dahliae. Thus, using site‐directed mutagenesis assays, we showed that mutations in CkPGIP1 and GhPGIP1 give rise to PGIP versatility, which allows evolving recognition specificities for PG and is required to promote Verticillium resistance in cotton by restricting the growth of invasive fungal pathogens. Significance statement: By using site‐directed mutagenesis assays, demonstrated that mutations in CkPGIP1 and GhPGIP1 give rise to PGIP versatility, which allows evolving recognition specificities for PG and is required to promote Verticillium resistance in cotton by restricting the growth of invasive fungal pathogens. [ABSTRACT FROM AUTHOR]

SUMMARY: On invasion of roots, plant‐parasitic nematodes secrete effectors to manipulate the cellular regulation of the host to promote parasitism. The root‐knot nematode Meloidogyne graminicola is one of the most damaging nematodes of rice. Here, we identified a novel effector of this nematode, named Mg16820, expressed in the nematode subventral glands. We localized the Mg16820 effector in the apoplast during the migration phase of the second‐stage juvenile in rice roots. In addition, during early development of the feeding site, Mg16820 was localized in giant cells, where it accumulated in the cytoplasm and the nucleus. Using transient expression in Nicotiana benthamiana leaves, we demonstrated that Mg16820 directed to the apoplast was able to suppress flg22‐induced reactive oxygen species production. In addition, expression of Mg16820 in the cytoplasm resulted in the suppression of the R2/Avr2‐ and Mi‐1.2‐induced hypersensitive response. A potential target protein of Mg16820 identified with the yeast two‐hybrid system was the dehydration stress‐inducible protein 1 (DIP1). Bimolecular fluorescence complementation resulted in a strong signal in the nucleus. DIP1 has been described as an abscisic acid (ABA)‐responsive gene and ABA is involved in the biotic and abiotic stress response. Our results demonstrate that Mg16820 is able to act in two cellular compartments as an immune suppressor and targets a protein involved in the stress response, therefore indicating an important role for this effector in parasitism. [ABSTRACT FROM AUTHOR]

Summary: Pathogenic fungi are emerging at an increasing rate on a wide range of host plants, leading to tremendous threats to the global economy and food safety. Several plant pathogens have been considered to be invasive species, rendering large‐scale population genomic analyses crucial to better understand their demographic history and evolutionary potential. Colletotrichum kahawae (Ck) is a highly aggressive and specialized pathogen, causing coffee berry disease in Arabica coffee in Africa. This pathogen leads to severe production losses and its dissemination out of Africa is greatly feared. To address this issue, a population genomic approach using thousands of single nucleotide polymorphisms (SNPs) spaced throughout the genome was used to unveil its demographic history and evolutionary potential. The current study confirms that Ck is a true clonal pathogen, perfectly adapted to green coffee berries, with three completely differentiated populations (Angolan, Cameroonian and East African). Two independent clonal lineages were found within the Angolan population as opposed to the remaining single clonal populations. The most probable colonization scenario suggests that this pathogen emerged in Angola and immediately dispersed to East Africa, where these two populations began to differentiate, followed by the introduction in Cameroon from an Angolan population. However, the differentiation between the two Angolan clonal lineages masks the mechanism for the emergence of the Cameroonian population. Our results suggest that Ck is completely differentiated from the ancestral lineage, has a low evolutionary potential and a low dispersion ability, with human transport the most likely scenario for its potential dispersion, which makes the fulfilment of the quarantine measures and management practices implemented crucial. [ABSTRACT FROM AUTHOR]

Summary: The type III secretion (T3S) system, an essential pathogenicity factor in most Gram‐negative plant‐pathogenic bacteria, injects bacterial effector proteins directly into the plant cell cytosol. Here, the type III effectors (T3Es) manipulate host cell processes to suppress defence and establish appropriate conditions for bacterial multiplication in the intercellular spaces of the plant tissue. T3E export depends on a secretion signal which is also present in 'non‐effectors'. The latter are secreted extracellular components of the T3S apparatus, but are not translocated into the plant cell. How the T3S system discriminates between T3Es and non‐effectors is still enigmatic. Previously, we have identified a putative translocation motif (TrM) in several T3Es from Xanthomonas campestris pv. vesicatoria (Xcv). Here, we analysed the TrM of the Xcv effector XopB in detail. Mutation studies showed that the proline/arginine‐rich motif is required for efficient type III‐dependent secretion and translocation of XopB and determines the dependence of XopB transport on the general T3S chaperone HpaB. Similar results were obtained for other effectors from Xcv. As the arginine residues of the TrM mediate specific binding of XopB to cardiolipin, one of the major lipid components in Xanthomonas membranes, we assume that the association of T3Es to the bacterial membrane prior to secretion supports type III‐dependent export. [ABSTRACT FROM AUTHOR]

Summary: Crop diseases cause significant yield losses, and the use of resistant cultivars can effectively mitigate these losses and control many plant diseases. Most plant resistance (R) genes encode immune receptors composed of nucleotide‐binding and leucine‐rich repeat (NLR) domains. These proteins mediate the specific recognition of pathogen avirulence effectors to induce defence responses. However, NLR‐triggered immunity can be associated with a reduction in growth and yield, so‐called 'fitness costs'. Recent data have shown that plants use an elaborate interplay of different mechanisms to control NLR gene transcript levels, as well as NLR protein abundance and activity, to avoid the associated cost of resistance in the absence of a pathogen. In this review, we discuss the different levels of NLR regulation (transcriptional, post‐transcriptional and at the protein level). We address the apparent need for plants to maintain diverse modes of regulation. A recent model suggesting an equilibrium 'ON/OFF state' of NLR proteins, in the absence of a pathogen, provides the context for our discussion. [ABSTRACT FROM AUTHOR]

Pine wilt disease (PWD) invaded southern Japan in the early 1900s and has gradually expanded its range to northern Honshu (Japanese mainland). The disease is caused by a pathogenic North American nematode, which is transmitted by native pine sawyer beetles. Recently, the disease has invaded other portions of East Asia and Europe where extensive mortality of host pines is anticipated to resemble historical patterns seen in Japan.There is a critical need to identify the main drivers of PWD invasion spread so as to predict the future spread and evaluate containment strategies in newly invaded world regions. But the coupling of pathogen and vector population dynamics introduces considerable complexity that is important for understanding this and other plant disease invasions.In this study, we analysed historical (1980–2011) records of PWD infection and vector abundance, which were spatially extensive but recorded at coarse categorical levels (none, low and high) across 403 municipalities in northern Honshu. We employed a multistate occupancy model that accounted both for demographic stochasticity and observation errors in categorical data.Analysis revealed that sparse sawyer populations had lower probabilities of transition to high abundance than did more abundant populations even when regional abundance stayed the same, suggesting the existence of positive density dependence, that is an Allee effect, in sawyer dynamics. Climatic conditions (average accumulated degree days) substantially limited invasion spread in northern regions, but this climatic influence on sawyer dynamics was generally weaker than the Allee effect.Our results suggest that tactics (eg sanitation logging of infected pines) which strengthen Allee effects in sawyer dynamics may be effective strategies for slowing the spread of PWD. This study presents a flexible multistate occupancy model that accounted both for demographic stochasticity and observation errors in categorical data. It has been applied to the rough but extensive survey records of the pine wilt disease, which is a world hazardous pest disease of pine forests. [ABSTRACT FROM AUTHOR]

Lettuce mosaic virus (LMV) is considered as the most destructive virus disease of lettuce. The presence of LMV was detected and LMV isolates were comprehensively characterized at molecular level in different parts of the world. While LMV infection was reported several times in different regions of Turkey, molecular characterization of LMV isolates lagged behind in Turkey compared to other regions of the world. For this purpose, surveys were carried out in Canakkale, Balikesir and Bursa provinces, and their districts which constitute South Marmara Region of Turkey in 2013-2015 lettuce cultivation seasons. A total of 307 samples were collected from lettuce plants showing symptoms of viral infection similar to LMV. The collected samples were tested with double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) to determine the presence of LMV. As a result of the tests, 35 of the 307 samples were infected with LMV. Out of 35 infected samples, 15 were selected considering the provinces and their districts where they were collected for further characterization. The coat protein (CP) genes of selected isolates were amplified with reverse transcription-polymerase chain reaction (RT-PCR) to determine the sequence variation in the CP gene of Turkish isolates. RT-PCR amplified CP genes of LMV isolates were cloned and sequenced. Similarity rates and phylogenetic relationships of South Marmara Region LMV isolates with each other and world LMV isolates obtained from GenBank databases were determined. The results showed that, identity rates of South Marmara Region LMV isolates were 96-100% and 89-99% at nucleotide level, and 97-100% and 93-100% at amino acid level among each other and with world isolates, respectively. In addition, phylogenetic analyses revealed that South Marmara Region LMV isolates were in the LMV-RoW (Rest of the World) group. [ABSTRACT FROM AUTHOR]

Abstract: Simple sequence repeats (SSRs) are preferred molecular markers because of their abundance, robustness, high reproducibility, high efficiency in detecting variation and suitability for high‐throughput analysis. In this study, an attempt was made to mine and analyse the SSRs from the genomes of two seed‐borne fungal pathogens, viz Ustilago maydis, which causes common smut of maize, and Tilletia horrida, the cause of rice kernel smut. After elimination of redundant sequences, 2,703 SSR loci of U. maydis were identified. Of the remaining SSRS, 44.5% accounted for di‐nucleotide repeats followed by 29.8% and 2.7% tri‐ and tetranucleotide repeats, respectively. Similarly, 2,638 SSR loci were identified in T. horrida, of which 20.2% were di‐nucleotide, 50.4% tri‐ and 20.5% tetra‐nucleotide repeats. A set of 65 SSRs designed from each fungus were validated, which yielded 23 polymorphic SSRs from Ustilago and 21 from Tilletia. These polymorphic SSR loci were also successfully cross‐amplified with the Ustilago segetum tritici and Tilletia indica. Principal coordinate analysis of SSR data clustered isolates according to their respective species. These newly developed and validated microsatellite markers may have immediate applications for detection of genetic variability and in population studies of bunt and smut of wheat and other related host plants. Moreover, this is first comprehensive report on molecular markers suitable for variability studies in wheat seed‐borne pathogens. [ABSTRACT FROM AUTHOR]

Rhizobium radiobacter formerly known as Agrobacterium tumefaciens, is the most important bacterial pathogen causing crown gall disease on over 750 different plant species including ornamentals, vegetables and fruit trees. This pathogen causes crown galls on root and stems of plants and rarely on, above-soil parts of plants. Biological control is successfully used in disease management; however, such strategies are quite ineffective in disease contaminated soils or seedlings. Thus, growers and scientists are mostly focused on disease resistant cultivars or rootstocks. In this study, crown gall disease reactions of three widely used rootstocks Garnem, Myrobolan and GF-677 for stone fruit trees were evaluated. A drop of bacterial suspension of 109 cfu mL-1 were inoculated onto three individual wounds over 90 shoots per rootstock. The weights and sizes of the tumor formed were measured five months after rootstock inoculations. The size of produced galls on rootstocks Garnem, Myrobolan and GF-677 were 0.16-5.28 mm, 0.09-4.42 mm and 0.09-0.36 mm, respectively. However, the weights of the galls varied between 0.02-2.85 g in Garnem, 0.01-1.58 g in Myrobolan and 0.02-0.11 g in GF-677 rootstocks. According to statistical analyses of gall formations, rootstocks were placed in different groups, additionally, none of them were found resistant to crown gall disease. Among the three rootstock tested, the study revealed that Garnem was highly susceptible, Myrobolan was moderately susceptible and GF-677 rootstock was less susceptible to crown gall disease. When an orchard will be intended to be newly planted with stone fruit trees, hence, GF-677 type rootstock would be a good choice to be preferred for planting in new orchards. [ABSTRACT FROM AUTHOR]